Carbon black is one of the darkest and most finely divided materials known. Chemically, carbon black is a colloidal form of elemental carbon consisting of 95 to 99 percent carbon. Made in specially designed reactors operating at internal temperatures in the range of 1425° C. to 2000° C., different grades of carbon black can be produced with varying aggregate size and structure.
In making tires and other rubber products, it is desirable to mix carbon black with an elastomer or rubber to improve certain properties of the elastomer. Most of the carbon black used in the tire industry is produced using the furnace process. In the furnace process, the feedstock is incompletely combusted in a reaction to form a very finely divided material composed of aggregates that are the carbon black monounits. These aggregates are typically submicron in size and of very complex structure. The surface of the aggregates may be covered with turbostratic graphitic crystallites and areas of disorganized amorphous carbon.
In order to produce different grades of carbon black, different reactor technology is sometimes employed. In addition to specific reactor design, the number and position of oil spraying nozzles, the ratio of air to feedstock and natural gas, as well as the position of the quench water sprays also plays a critical role in setting the carbon black properties (size, surface area, and structure). When carbon black is formed in the reactor, which takes only a few milliseconds, it is in the form of a thick smoke with apparent density of about 10−2 g/cm3. The remaining production time, which could be up to two hours, is conveying and handling the product in order to prepare the carbon black to be shipped and further processed.
There is a continuing need for a carbon black product with surface modification that facilitates dispersion in rubber formulations, and which provides superior compression set characteristics in cured rubber products. Desirably, the surface modification of the carbon black product may be performed in situ in a carbon black reactor during the manufacturing of the carbon black product.